Large vessels such as container ships and tankers on ocean passage consume large amounts of fuel. The large consumption of fuel constitutes a considerable increasing percentage of shipping companies' expenses due to increasing oil prices. Also from an environmental point of view the large consumption of fuel for transportation of goods by vessels is a problem. Accordingly, it is desirable to reduce vessels' fuel consumption and increase vessels' propulsion efficiency.
EP0551367 discloses a method for achieving optimum utilization of engine power to a ship's propeller, where a computer is used in a regulating loop which continuously controls the power by regulating the output from the ships engine, and optionally regulating the pitch angle for the propeller blades, as well as the number of revolutions of the propeller shaft, so that the longitudinal net force in the propeller shaft is monitored continuously by a force sensor and used as a main parameter for controlling the power, in such a manner that the net force is all the time optimized in relation to propeller efficiency and economic engine fuel consumption. The method of EP0551367 may be disadvantageous since it requires the use of a device for monitoring the longitudinal net force in the propeller shaft.
Whereas EP0551367 discloses a method that aims at improving propeller efficiency, it would be advantageous to improve vessels' efficiency even further by use of alternative methods for propeller control.